This invention relates to carotid endarterectomy surgery. More particularly, it relates to methods and apparatus for improving endarterectomy procedures by using blood filtration to protect the patient from embolization during these vascular surgeries.
Endarterectomy is a surgical procedure which generally includes the removal of the lining of an artery. Typically, the artery is dissected longitudinally to expose an affected region from which plaque and other materials may be removed. Endarterectomy can be performed on almost any major artery that is diseased or blocked, and is most commonly used for the carotid, femoral, and popliteal arteries.
In a typical procedure, the surgeon makes a standard vertical incision in the neck of a patient, or a transverse incision corresponding to a skin line of the neck. The incision is deepened through and around subcutaneous adipose tissue, platysma muscle, the branches of the external jugular vein, and the border of the sternocleidomastoid muscle in order to expose the carotid sheath. Careful dissection is used to expose the common carotid artery and its external and internal branches. Vascular clamps are applied to the internal carotid artery, external carotid artery, and common carotid artery, and a vertical arteriotomy is made in the common carotid artery, typically below the bifurcation. The incision may be advanced into the internal carotid artery to a point beyond the area which contains plaque material.
An indwelling shunt may then be installed in order to bypass the clamped region of the artery so that brain perfusion is not disrupted. The artery is then clamped proximal and distal about the shunt in order to isolate a bloodless region for endarterectomy. Atheromatous material is then removed, first from the common carotid artery, then from the external carotid artery, and generally last from the internal carotid artery. After the endarterectomy procedure has been performed, the surgeon cleans the region of plaque fragments before removal of the shunt and closure of the vascular incision.
The above-described procedure, however, suffers from a deficiency which relates to the escape of embolic material which may lead to devastating neurologic complications, particularly when emboli escape through the internal carotid artery. Emboli may be produced through any step of the procedure where mechanical forces are applied to the artery, and these manipulations include clamping, unclamping, applying a tourniquet, dissecting the vessel, inserting and removing a bypass shunt, removing atheromatous material, cleaning the affected site, and suturing the vessel. Therefore, a need, exists for an improved endarterectomy procedure and apparatus which will enable the surgeon to minimize the production of embolic material and to prevent the escape of embolic material during carotid endarterectomy, arteriotomy, and other vascular surgeries.
A dramatic improvement in the neurologic outcome of patients undergoing carotid endarterectomy, and arteriotomy procedures generally, can be achieved by using a blood filter device to capture and remove dislodged embolic material during the surgical procedure in accordance with our invention. Thus, the invention provides novel methods and apparatus for protecting a patient from embolization during arteriotomy procedures. In one embodiment, the invention provides a bypass tubing or indwelling shunt, having a main lumen for blood bypass and a second, branching lumen adapted to receive an elongated blood filtration instrument, or other surgical device (e.g., an angioplasty catheter, stent catheter, atherectomy catheter) and to allow passage of same into an artery distal to the endarterectomy region. The branching secondary lumen can either merge and communicate with the main lumen of the shunt, or may extend to a distal opening separate from the blood bypass lumen of the device.
In another embodiment, a standard single-lumen indwelling shunt is used in accordance with the disclosure of Loftus, Carotid Endarterectomy Principles and Techniques; Quality Medical Publishing, Inc.; St. Louis, Mo., 1995 (this and all other references cited herein are expressly incorporated by reference as if fully set forth in their entirety herein), and an introducer sheath and filtration catheter are provided for deployment distal to the site of standard carotid endarterectomy. The introducer sheath includes a hemostatic valve adapted to receive a filtration catheter. The filtration catheter typically includes a catheter sheath, an elongated control member, a control mechanism at a proximal end of the control member, and a filtration assembly which includes an expansion frame and filter mesh at a distal region of the control member, the expansion frame being operable to enlarge from a contracted condition to an expanded condition which covers all of, or a substantial portion of the cross-sectional area of a vessel. In alternative embodiments, a filter is disposed on a guidewire or tubing for use in carotid artery bypass to capture clots and atherosclerotic material released during endarterectomy.
According to the methods of the present invention, an affected region of an artery is isolated, clamped, and dissected as disclosed in Loftus, Carotid Endarterectomy Principles and Techniques; Quality Medical Publishing, Inc.; St. Louis, Mo., 1995, and Smith, The Surgical Treatment of Peripheral Vascular Disease, Chapter 142, in xe2x80x9cThe Heart, Arteries, and Veins,xe2x80x9d Vol. 2, Ed. J. Willis Hurst; McGraw-Hill Information Services Corp., 1990. An indwelling shunt as described herein is then inserted so that the distal region penetrates into the distal artery and is secured by a distal artery clamp, while the proximal region penetrates into the proximal artery and is secured by a clamp proximal to the region of arteriotomy. A blood filter device is deployed through the second lumen of the indwelling shunt as disclosed herein, is advanced within the blood vessel, and then expanded to cover a substantial cross-sectional area of the artery distal to the arteriotomy region. Endarterectomy is performed in accordance with standard procedures to remove atherosclerotic material from the affected region of the artery.
According to an alternative method, a non-indwelling shunt or plastic tubing as disclosed herein is used to bypass an affected region of the artery. After the carotid artery is exposed, an incision is made proximal to the site where the common carotid artery cross-clamp will be placed. Plastic tubing having an appropriate size is placed in this incision and then extended distally, past the site where the internal carotid artery cross-clamp will be placed, and distal to the atherosclerotic plaque, where the plastic tubing reenters the carotid artery through a second incision. A filter device is deployed in the internal carotid artery through a side-port on the shunt, or the filter may be deployed by an expansion mechanism intrinsic to the tubing itself. The common and internal carotid arteries are then clamped. The carotid artery is incised, plaque removed, the operative site rinsed with sterile saline or water, and the carotid artery, with or without a graft, is closed. The proximal and distal cross-clamps are removed, and circulation through the repaired carotid artery is restored as discussed herein. The proximal end of the plastic tubing is removed from the common carotid artery and the proximal incision is closed. The filter, including captured embolic material, is retracted after several minutes, typically at least 5 minutes, more preferably at least 10 minutes, and the distal end of the shunt is removed. Finally, the distal incision is closed.